This invention relates to the salvaging of used and or defective dosimeters for subsequent reliable use.
Dosimeters are now often discarded after extended use by personnel or exposure to significant doses of gamma radiation. Such personnel dosimeters also become damaged and unreliable after long storage periods so as to provide distorted readings varying between zero and excessively high dose reading values following either no exposure to gamma radiation or moderate exposure. Presently available procedures of pre-dose screening and/or light detergent washing of the dosimeters inadequately deal with such reading reliability problems.
In so far as prolonged storage is concerned, dosimeter damage often occurs as a result of humid environmental conditions. Moisture condensation on the exposed faces of the dosimeter sensing elements causes chemical and physical changes. Thus, surface projection growths and pitting occurs as a result of such chemical changes to optically affect the sensing operation of the dosimeters after ultra-violet irradiation to induce emissions indicative of prior exposure to gamma radiation. Distortion of readings indicative of such gamma radiation exposure accordingly results from the referred to humidity caused surface degradation damage.
The evaluation of dosimeters, having sensing elements of the phosphate glass type, to avoid reading errors is already generally known, as referred to for example in U.S. Pat. No. 4,333,013 to Burgkhardt et al. The use of ultra-violet radiation for inducing luminescent emissions by excitation of phosphors, is also known as disclosed for example in U.S. Pat. No. 3,793,527 to Forest while the visual inspection of luminescent materials for observance of surface degradation following exposure to radiation is referred to for example in U.S. Pat. No. 4,802,762 to Hill, Jr. However, the prior art referred to in the latter U.S. patents does not deal with the correction of error producing changes in the sensing elements of dosimeters such as those of the phosphate glass type referred to in the Burgkhardt et al. patent, aforementioned.
It is therefore an important object of the present invention to avoid the periodic discarding of large numbers of personnel dosimeters of the foregoing type, heretofore deemed to be unsalvagable.
Yet another object of the present invention, in accordance with the foregoing object, is to provide for the repair and refurbishment of defective dosimeters made unreliable or useless by prior radiation exposures and/or prolonged storage under humid conditions.